The present invention relates to optical scanners, and more specifically to a multiple depth of field laser optical scanner.
Optical scanners are well known for their usefulness in collecting and processing information within bar code labels. Optical scanners that generate scan patterns made up of intersecting lines typically employ a laser, a mirrored spinner, and a photodetector. The laser emits a laser beam which is reflected by the mirrored spinner to form the lines of the scan pattern. The photodetector collects light reflected from items having bar code labels and converts the reflected light into electrical signals based upon its intensity.
The depth of field of laser optical scanners is limited by diffraction of the laser beam. The waist size of the beam is only small enough to resolve the bar code transitions over a small depth of field. Typically, the depth of field of a laser optical scanner which must read a bar code label with a 0.013-inch transition spacing is only about six inches. The depth of field for reading higher density (lower transition spacing) bar code labels is even less.
Therefore, it would be desirable to provide a multiple depth of field laser optical scanner which can read bar code labels located within a range of distances from the scanner.